Conversion of invert molasses



United States Patent 25,745 CONVERSION OF INVERT MOLASSES Robert E. Jones, North Muskegon, Mich., and Henry B. Lange, Scotch Plains, N.J., assignors to Merck & (10., Inc., Rahway, NJ., a corporation of New Jersey No Drawing. Original No. 3,066,150, dated Nov. 27, 1962, Ser. No. 706,594, Jan. 2, 1958. Application for reissue Sept. 16, 1964, Ser. No. 410,338 2 Claims. (Cl. 260347.8)

I Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

This invention relates to the conversion of sugar to S-hydroxymethyl furfur-al (HMF), and has for its object the provision of an improved process for the treatment of invert molasses to separate the ionic material from the sugar, and the conversion of the resulting product containing higher purity sugar into HMF.

In the conversion of sugars in aqueous solution at elevated temperatures an acid catalyst is necessary to achieve an eflicinet yield in a relatively short time. Although invert molasses provides a supply of inexpensive sugar in aqueous solution, we have found it to be impractical to convert the sugar to HMF because of the contained cations and organic acids. The molasses contains various in organic compounds including calcium salts, and such organic acids as succinic, aconitic and malic, which are ionic materials. The yield of HMF in converting the sugar of molasses to HMF according to the process of the [copending] application of John D. Garber and Robert E. Jones, Serial No. 624,224, filed November 26, 1956, now U.S. Patent 2,929,823, is generally satisfactory, but the organic acids appear to react with the HMF and form products which seriously impair its purity. Moreover, the cations, such as calcium and sodium, react with the acid catalyst forming an intractable solid or sludge which not only destroys the catalyst but plugs the reactor. When sulfuric acid or a sulfate such as aluminum sulfate is used as the catalyst this solid is probably calcium sulfate.

This invention is based on our discovery of a very simple and efficient process for the removal from the molasses of the cations and organic acids forming a purified invert molasses from which we can form HMF in high purity from this inexpensive source of sugar. In accordance with our invention we pass the molasses through a bed or column of a cation exchange resin, and by the ion exclusion technique separate in aqueous solution the ionic cations and organic acids from the solution of nonionic sugar. By selecting a resin having the proper particle size, and porosity as represented by its crosslinking, the aforementioned solutions can be separated from molasses by fractionation. The resin sold by the Dow Chemical Company under the name Dowex 50 (X-2) [which] is a [phenolic methylene sulfonic acid] sulfonated styrene type resin copolymerized with divinylbenzene 0f the kind disclosed in U.S. Patent 2,588,389 which has the cross-linkage and porosity to effect a separation of the ionic material from the sugar by ion exclusion. In the above trademark, the X represents the percent of divinylbenzene in the copolymer and it is a mere detail to select the resin which is most efiicient for the ion exclusion treatment of invert molasses. The ion exclusion technique is important in our process for the following reasons:

(1) No chemicals are consumed on regeneration of the resinonly Water (and power for pumping) are consumed;

(2) A fair degree of decolorization occurs on the ion exclusion column; and

Re. 25,745 Reissued Mar. 23, 1965 (3) The salts of the organic acids (many worth recovering in heavy production) come out in definite cuts and can be stored for other uses.

With each resin having a certain average particle size and porosity there are volume relationships that are important in the ion exclusion process. These are the volume within the resin itself, and the interstitial volume which is the space between the particles of resin. When the molasses is passed through the resin the ionic material appears as soon as the influent volume equals the interstitial volume and soon reaches its initial concentration. The non-ionic sugar solution does not appear until the influent volume reaches the sum of the two volumes and soon reaches its peak concentration. The invention is accordingly practiced by separating the first fraction containing the ionics which is low in sugar from the last fraction which is low in ionics and high in sugar.

In carrying out an operation of the invention a molasses containing about sugar is preferably diluted with water to about 57 to 58% sugar to provide a solution which will flow freely through the column of ion exchange resin. Into a column, for example 2.8 cm. in diameter, was slurried 298 cc. of Dowex 50 (X-Z), using a standard sodium chloride solution for mobilizing, giving a resin bed 49 cm. deep. Salt washing was continued until the efiluent showed neutral pHat this point the column was on the sodium cycle. The column was next washed with Water until the chloride ion was displaced. In this treatment the resin swells about 50%, and this part of the operation may be done in a separate batch or container.

The sugar solution for the operation was made from 51 grams of molasses containing 38.2 grams of sugar which was diluted with 15 cc. of water. Three separate runs of this solution were passed through the column. Then the operation was started by passing the solution at the rate of 4.1 cc./min. through the column. The cuts and their compositions thereof are described in the following tab e:

TABLE 1 No. Volume Specific Wt. Na Test Remarks cc. Gravity Sugars, g.

a 175 Clear iorerun. 1 50 0. 999-1. 000 Yellow sol'n. 2 25 1. 001-1. 002 Brownyellow soln. 25 1. 003 Dark brown soln. 25 1.006 Do. 25 1. 010 0. D0. 25 1.019 1. Do. 25 1. 030 2. D0. 25 1. 038 2. Brownyellow soln. 25 l. 050 3. 33 25 1. 069 4. 60 1. 085 5. 67 1. 091 6. 05 1.088 5. 1. 068 4. 53 1. 039 2. 65 1. 014 1. 00 1.005 Do. Clear column wash.

The differences in the sugar balance (6%) is probably due to the temperature differences in specific gravity measurements made on the solutions.

The cuts were obtained by collecting the samples in series one after another until the entire mass of solution was passed through the column. The diiferences in the composition from cut to cut are due to some concurrent passage of ionic and nonionic materials. In practice, the first part of the run, say, consisting of the collected material of cuts 18, is discarded, or saved for recovery of the contained chemicals, as containing most of the ionics and an unimportant amount of sugar. The combined material of cuts 9 to 16 is collected as containing most of the sugar in a relatively pure state. The tests for sodium by the flame and zinc uranyl acetate methods 5 of the combined cuts 9 to 16 showed the sodium content to be low and the sugar to be 88% of the total sugar.

The combined cuts 9 to 16 were used as a product for conversion to HMF by the process described and claimed in the said application of John D. Garber and Robert E. Jones. This application describes a continuous process for the conversion of sugar in aqueous solution to HMF at temperatures of from 250 to 380 C. with an acid catalyst, and the separation of the HMF as quickly as possible to minimize its decomposition. The process is carried out advantageously by passing the sugar solution rapidly through heated tubes and the separation of the HMF in a suitable solvent.

For the conversion of the sugar of the purified molasses to HMF, aluminum sulfate was added to the sugar solution as catalyst, and the solution containing 15.8% sugar was treated in sealed capillary tubes for conversion of the sugar to HMF. The tubes of the type which are used for melting point determinations are especially suitable for such tests. These tubes were filled with from 4060 mg. of the solution the ends of which were sealed by fusion. The sealed tubes were heated in an oil bath held at a constant temperature of about 270 C. for the desired time which was about 8 to 13 seconds. The tubes were quickly removed from the oil and plunged into a cold oil bath. Then the tubes were smashed in volumetric flasks. The conversion to HMF was estimated by determining U.V. absorption at 2830" A.

The results of the conversions in six capillary tubes, run at various contact times, and the HMF yields, are listed in the following table.

Run Time, Percent Ratio sec. HMF

The HMF yield on this material is nearly standard in that the highest yield thus far obtainable using crystalline sucrose is 52%. Two points are worthy of note: (1) the purity is slightly below standard, as judged by the ratio, and (2) the contact time for maximum yield is slightly longer than with 25% sucrose solutions.

The ratio used to judge purity of crude HMF in solution is optical density at 2830 m divided by optical density at 2290 my. For pure HMF, the ratio is 5.7-5 .9.

The invert molasses contains bufier salts which cancel the effect of the acid catalyst for conversion of the sugar to HMF by heating aqueous solutions thereof to temperatures of from 250 C. to 280 C. as aforementioned. The removal of the buffer salts permits the HMF formation catalysts to operate.

We claim:

1. The process for the conversion of the sugar of invert molasses to S-hydroxyrnethyl furfural which comprises passing the molasses solution through a bed of granular cation exchange resin [of the phenolic cross-linked sulfonic acid type] of the type comprising sulfonated styrene polymer copolymerized with divinylbenzene on the sodium cycle to separate from the molasses solution by ion eX- clusion a solution containing the ionic cations and organic acids and a solution containing the major portion of the sugar which is relatively free of such cations and organic acids, and heating the solution of sugar to a temperature above 250 C. in the presence of an acid catalyst to form the S-hydroxymethyl furf-ural.

2. In the process of claim 1, heating the sugar solution to a temperature in the range of 250 C. to 380 C. while passing the solution continuously through a tube, and then rapidly cooling the solution and separating the 5 -hydroxymethyl furfural.

References Cited by the Examiner The following references, cited by the Examiner, are of record in the patented file of this patent or the original patent.

UNITED STATES PATENTS 2,750,394 6/56 Peniston 260-3478 FOREIGN PATENTS 591,858 9/47 Great Britain. 600,871 4/48 Great Britain.

NICHOLAS S. RIZZO, Primary Examiner. 

1. THE PROCESS FOR THE CONVERSION OF THE SUGAR OF INVERT MOLASSES TO 5-HYDROXYMETHYL FURFURAL WHICH COMPRISES PASSING THE MOLASSES SOLUTION THROUGH A BED OF GRANULAR CATION EXCHANGE RESIN (OF THE PHENOLIC CROSS-LINKED SULFONIC ACID TYPE) OF THE TYPE COMPRISING SULFONATED STYRENE POLYMER COPOLYMERIZED WITH DIVIDYLBENZENE ON THE SODIUM CYCLE TO SEPARATE FROM THE MOLASSES SOLUTION BY ION EXCLUSION A SOLUTION CONTAINING THE MAJOR PORTION OF THE ACIDS AND A SOLUTION CONTAINING THE MAJOR PORTION OF THE SUGAR WHICH IS RELATIVELY FREE OF SUCH CATIONS AND ORGANIC ACIDS, AND HEATING THE SOLUTION OF SUGAR TO A TEMPERATURE ABOVE 250* C. IN THE PRESENCE OF AN ACID CATALYST TO FORM THE 5-HYDROXMETHYL FURFURAL. 